Pusan National University Study Identifies Smarter Cooling Strategy for Liquid Hydrogen Tanks

­Hydrogen is a promising clean energy carrier, but storage remains challenging. Cooling it to approximately 20 K (-253 ℃) produces liquid hydrogen with about 800 times the volumetric energy density of hydrogen gas. Even small heat leaks can cause evaporation, increasing tank pressure and reducing storage efficiency.

Conventional insulation materials such as multi-layer insulation, polyurethane foam (PUF), and glass bubbles reduce heat transfer but have limitations. The cryogenic sacrificial liquid (CSF) concept proposed by the Korea Research Institute of Ships and Ocean Engineering (KRISO) uses externally supplied LNG or LN2 in channels to intercept heat before it reaches the inner vessel.

To optimize this approach, a research team led by Professor Jong-Chun Park of PNU's Department of Naval Architecture and Ocean Engineering in South Korea evaluated a semi-active CSF-assisted insulation system for a KRISO-designed marine Type-C liquid hydrogen (LH2) storage tank. Here, "sacrificial" means that the secondary coolant absorbs the heat before the hydrogen does; the fluid is intended to be reliquefied and recirculated rather than discarded. "The key is to intercept heat before it reaches the liquid-hydrogen vessel," explains Prof. Park. "By controlling the flow and placement of the channels, we can direct more of the incoming heat into the secondary coolant." The article was published online on April 08, 2026, in Energy Conversion and Management and appears in Volume 357, dated June 01, 2026.

Using a three-dimensional model that coupled heat conduction through the tank with multiphase flow and wall boiling inside the CSF channels, the researchers evaluated the effects of channel size, mass flow rate, number, and placement on heat ingress and coolant vaporization.

The simulations showed that, without active CSF circulation, more than 85% of the heat entering the tank traveled through the structural supports rather than the insulation layers, making the supports the dominant thermal bridges. Positioning cooling channels along these supports and extending them to the head-shell junction reduced heat ingress more effectively than distributing channels elsewhere, demonstrating that placement mattered more than channel count.

The study also found that increasing channel size eventually produced diminishing returns, with a channel-to-tank diameter ratio (d/D) near 0.04 marking the onset of saturation. In the best layouts, simulated total heat ingress decreased by 43.6% with LNG and 66.5% with LN2. While LN2 provided greater cooling because of its lower temperature, it was more prone to vapor generation, whereas LNG delivered a smaller but more stable cooling effect. The researchers also found that stronger local heat transfer inside a channel did not necessarily improve overall insulation because performance depended on where the heat was redirected and how much coolant vaporized.

"Our findings show that effective LH2 storage is not simply a matter of adding thicker insulation or more cooling channels," notes Prof. Park. "The largest gains came from identifying the tank's thermal bridges and placing cooling exactly where the heat entered. Smarter placement, not simply more material, was the key." He adds, "This provides a practical design strategy for balancing thermal performance, coolant stability, and system complexity."

The findings provide practical guidance for improving liquid-hydrogen storage systems. Although the results are specific to the modeled KRISO tank under steady-state conditions, experimental validation and transient analyses are needed before practical deployment.

Reference
Title of original paper: Design and evaluation of cryogenic sacrificial fluid-assisted insulation for boil-off reduction in liquid hydrogen Type-C tanks
Journal: Energy Conversion and Management